I had that exact problem when I upgraded to LED bulbs. The cruise control uses the incandescent bulbs filament for the ground path. You have to slightly modify your clutch switch wiring in order for the cruise control to work. 
Mike M

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On Dec 18, 2014, at 11:30 AM, Stan Shapiro <mail@STANSHAPIRO.COM> wrote:

> 
> anyone have any experience with LED brake light bulbs causing a problem with factory cruise control on 90 Westy?  Interfering with the brake lite aspect of the cruise circuitry?
> 
> Stan
>